Safety device for setting off explosive charges



Sept. 5, 1949.

SAFETY DEVICE R. G. MARTIN FOR SETTING OFF EXPLOSIVE CHARGES Filed Sept.19, 1947 Patented Sept. 6, 1949 SAFETY DEVICE FOR' SETTING. OFF

EXPISOSIVE cannons Russell, G., Martin, Russcllvillc, Va. ApplicationSeptember 19, 1947 Serial 174,924 3 Claims. (01. 175-115).

This inventionrelates: toiignition devices for explosives andrmore;particularly to. a pportable ignition: device. for use; inlmines, andthe like tor setting off explosive charges;

A main object: of'the invention-is. torprovide a noveluandiimprovedsafety device for setting. oi charges of explosive which isvery simpl'einxcon strnction compact in size, andlreliable inopera tion A further:objector; the invention is to provideanimproved safety devicerfor' usein-mining operations; and the. like, in setting oi-i' explosive chargesrsaid. device containing the source of current:v for-igniting the.explosivev and being ar= ranged so: that the, explosive cannotaccidentally be. set .ofiifwhile; the-wiring connections thereof arebeingzm-ad'e: to the: device, thereby reducing hazards to miners, andlatthe same time, providing effective control of the ignition ofthe'explosi ve;

Further objects and advantages :of the invention. will: become apparentfrom: the following description and* claims; and from the accompanyin'g. drawings, wherein:

Figure 1 is an elevational view showingasafety explosive ignition deviceconstructed in accordance with the present invention, the hinged coverof the device being shown in open position.

Figure. 2 is atop view of the ignition device of Figure 1 with the coverin closed position.

Figure 3 is an enlarged cross-sectional detail view taken"on-line3'-3'of Figure 1.

Referring to the drawings; tldesignates-agen orally rectangularhousing,preferably of insulatin-g, material; provided, with a; cover 6 2, hinged-to the housing at l3, l3. Received in the housing ii are a pair offlashlight battery cells it and i5, cell l being inverted, as shown inFigure l. Secured to the bottom wall of housing I i beneath the cells I4and I5 is a U-shaped contact spring I6 which engages the bottom of themetal casing of cell [4 at one arm thereof and engages the centerpositive pole contact of the inverted cell l5 at the other arm thereof.

The top wall of housing I l is apertured immediately above the centerpositive pole contact of the cell l5 and secured to said top wall aroundthe aperture therein is a metal washer ll. Passing slidably through thewasher is the shank of a headed bolt or pin is to the bottom end orwhich is secured a collar member l9, preventing upward removal of thebolt l8 from the washer H. A coiled spring 29 encircles the shank ofbolt l8 and bears between the head of the bolt and washer ll, therebybiasing the bolt upwardly. When bolt is is manually depressed, thebottom notches 30 and end thereof engages the center positive pole con?tact of cell Mi Secured to the top wall of housing H by a: bolt 2iisanangle bracket 22, and pivotally secured to the upstanding arm ofbracket 22 is a lever bar 23 which is swingable in a transverseverticalplane of housing H. The angle bracket 22 is locatedvadjacent'the front edge of said top wall, and secured to saidtop walladjacent its rearedge is a second angle bracket 24. Pivotally securedto, the upstanding arm. of bracket 24 is a lever bar 25' which isswingable in, the same transverse vertical plane as lever: bar 23.Secured to the top wall of housing H between the angle brackets til-and24 is an upstanding boss26 of insulating material, and secured to, thetop of. said'boss in th transverse plane of lever arms, 2'3. and; 25 isa metal bar 2], the ends or said bar 2i being normally spaced from thelever bars 23' and 25.,by the biasing action of respective coiledsprings 28 and 23- which bear between suitable recesses formed in boss25 and the adjacent inner edge portions of the respective lever bars 23and 25. The bottom ends of the lever bars bear against the top wall ofthe housing, thereby limiting outward rotation of the lever bars underthe biasing force exerted thereon by the springs 28 and 29. The upperportionsof the outer edges of the lever bars 23 and 25 are formed withrespective arcuate 3|- providing finger engaging means for rotating thelever bars inwardly. By exerting squeezing pressure on said lever barswith the fingers, the lever bars are simultaneously brought into'contactwith the ends of the bar 21.

Secured to the bottom surface of the housing top wall by bolt 2| is abowed contact spring 32 which engages the bottom of the metal casing ofthe inverted cell It. Secured to the top wall of the housing H betweenwasher I1 and boss 26 is a transverse terminal block 33 of insulatingmaterial provided with spaced terminal jacks 34 and 35. Washer I! isconnected to terminal jack 34 by a wire 36 and bracket 25 is connectedto terminal jack 35 by a wire 31. The external ignition element, notshown, is connected to the jacks 34 and 35 by wires 38 and 39 providedwith male prongs which are plugged into the respective jacks.

When the charge of explosive is to be detonated, lever arms and 3| aresqueezed together with the fingers so that they engage the ends of bar21, and the head of bolt I8 is pushed downwardly so that its bottom endengages the center positive terminal of cell [4. This completes thedetonating circuit, said circuit comprising wire 38, jack 34, wire 36,washer l7, bolt l8, cell l4, spring I 6, cell l5, contact spring 32,bolt 2 I, bracket 22, lever arm 23, bar 21, lever arm 25, bracket 24,wire 37, jack 35, and wire 39.

It is to be noted that the detonating circuit is normally open at threepoints, namely, at lever arm 23, at lever arm 25 and at contact bolt is,so that accidental detonation cannot occur when the wires 38 and 39 areconnected to the jacks 34 and 35.

The cover l 2 is normally secured in closed position by a hook latch 49pivotally connected thereto which is engaged with a pin 4| projectingfrom the side wall of housing I l.

While a specific embodiment of an ignition device for setting ofiexplosive charges has been disclosed in the foregoing description, itwill be understood that various modifications within the spirit of theinvention may occur to those skilled in the art. Therefore it isintended that no limitations be placed on the invention except asdefined by the scope of the appended claims.

What is claimed is:

1. A portable shot firer comprising an insulated box-like casin havingtop and bottom Walls, a pair of vertically disposed dry battery cellsarranged in inverted, side by side position in said casing andsubstantially filling the space between lower ends of said cells, aspring retracted plunger contactor mounted on and operating through saidtop wall, said contactor being arranged to engage the upper terminal ofone of said cells when depressed, a pair of laterally spaced levercontactors pivotally mounted on said top wall to swing inwardly towardeach other from outward starting poistions, a bridging block mounted onsaid top wall between said levers, spring means normally yieldablymaintaining said levers in their outward tactors, a pair of jacksmounted on said top wall, and means severally connecting the remaininglever contactor and said plunger contactor with an electrical detonatorconcan be detonated only while said plunger contact is held in depressedposition and both of said lever contactors are held inwardly againstsaid bridging block.

2. A portable shot firer comprising an insulated battery case containingbattery means having a. pair of terminals, 2. spring retracted plungercontactor on said case engageable only in its inpressed position withone of said terminals, a pair of lever contactors, means pivoting saidlevers for movement toward and away from said other, spring meansnormally maintaining said levers yieldably in spread relation, abridging block on said case between said levers with which said leversare out of contact in their normal spread positions, means connectingone of said lever con- .tactors with the other terminal of said batterymeans, and a pair of jacks on said case severally connected to theremaining lever contactor and said plunger contactor, whereby anelectrical detonator connected to said jacks can be detonated only whilesaid plunger contact is held in in-pressed position, and both of saidlever contactors are held in inward positions in engagement with saidbridging block.

3. A shot firer comprising an insulated sup port, a spring retractedplunger contactor on said support, a contact with which said plungerconently swingable between their normal spread positions and theirinwardly swung positions, a pair of jacks on said engagement with saidbridging block.

RUSSELL G. MARTIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Date

